Axial fed nu-sided cavity with triggering control for selectively energizing individual faraday rotator switches for multi-channel communication



3,155,925 L FOR E. WANTUCH Nov. 3, 1964 AXIAL FED N-SIDED CAVITY WITH TRIGGERING CONTRO SELECTIVEZLY ENERGIZING INDIVIDUAL FARADAY ROTATOR SWITCHES FOR MULTI-CHANNEL COMMUNICATION Filed Dec. 18, 1961 2 Sheets-Sheet l INVENTOR 2 773652 fi flzzzo,

BY W6. 404.1,

ATTORNEZE Nov, 3, 1964 a WANTUCH 3,155,925

AXIAL FED N-S-IDED CAVITY WITH TRIGGERING CONTROL FOR SELECTIVELY ENERGIZING INDIVIDUAL FARADAY ROTATOR SWITCHES FOR MULTI-CHANNEL COMMUNICATION Filed Dec. 18. 1961 2 Sheets-Sheet 2 4 if 1mm I 4 b j? 3d 7 INVENTOR ATTORNEY5 United States Patent Ofi fice 3 ,155,925 Patented Nov. 3, 1964 AXEAL FED N SEDED CAVITY WITH TREGGERENG CGNTROL FGR SELEQTEVELY ENERGIZING IN- DIWDUAL FARADAY ROTATGR SWETQHES FQR MULTl-QHANNEL CGMMUNIQATEQN Ernest Wantuch, Livingston, NJ assignor to Airtron, inc, Morris Plains, NJ. Filed Dec. 18, 1961, er. No. 159,866 4 Claims. (El. SSS-7) This invention generally relates to microwave switches, and more particularly to multiple channel microwave switches for rapidly and selectively connecting a highfrequency microwave signal to any one or" a plurality of different signal transmission channels with low-loss transmission of the signal through the switching mechanism.

The invention is particularly concerned with rapidly commutatin a microwave signal from an input transmission path selectively over any one of a plurality of output paths rapidly and with low transmission loss. By analogy with lower frequency electrical switching means, the system may be termed a single-pole multiple throw switch.

According to one preferred form of the invention, a switching mechanism is comprised of a plurality of microwave switch arms each having a configuration known as a tetrahedral switch, with each switch arm having a ferrite or Faraday type element therein which when energized permits the passage of a signal through the switch with low loss, and when deenergized eir'ectively blocks the signal. These plurality of switches are physically and electrically interconnected in a unique arrangement by means of a junction to be commonly and equally excited by the microwave signal to he coniinutated. A triggering system is provided to rapidly and selectively energize only the ferrite element in the particular switch channel selected thereby to ccmmutate the signal only over the channel desired. Because of the low loss andrapid switching times involved, a plurality of such multiple switching systems may be interconnected in various cascaded banks, permitting a considerable number of commutatlng paths to be selectively connected to the common input microwave channel.

it is accordingly a principal object of the invention to provide an improved multiple-channel or multiplepole switching means for commutating a microwave signal.

A further object is to provide such a means employing Faraday-optical elements, such as ferrite, and having no mechanical moving parts.

Still another object is to provide such a mechanism that may be commutated rapidly and with very low power loss or distortion of the signal.

A still further object is to provide such a switching system that is properly matched electrically and mechanical-ly to the input source, thereby to permit commutation or" the microwave signal over any one of a plurality of dillerent paths without adversely affecting the source.

ther objects and advantages will be readily apparent by those skilled in the art after a detailed consideration or" the following specification and accompanying drawings wherein:

FIG. 1 is a perspective view of one preferred switch a triggering system for operating the switch mechanism of FIG. 1;

IG. 4 is a schematic electrical diagram illustrating a preferred driver circuit that may be employed in the triggering system of FIG. 3; and

FIG. 5 is an electrical line diagram illustrating one manner of cascading the switch mechanisms for multiplying the number of commutation paths that may be obtained.

Referring now to the drawings, there is shown in FIG. 1 one preferred multipole microwave switch or commutator according to the invention wherein an input microwave signal being directed over a coaxial input line it may be selectively transmitted over any one of four different output waveguide channels, 12 to 14, inclusive, as desired, by selectively energizing one of the output channels by a control signal.

The overall switching mechanism as shown generally comprises a coax to waveguide transition in the form of a junction ill. The junction 16) contains four sym metrically positioned outlet ports, such as 17, and 18, as shown, each being located in a difierent vertical side wall of the four-sided junction member, and each outlet port being isolated from the others and properly matched so that the input power from the microwave signal is divided to equally excite all of the outlet.

ports. To provide the electrical symmetry required, the central axes of the tour outlet ports lie in a common horizontal plane and the axes intersect one another at the common central point interior of the junction. The input microwave signal over line 20 is introduced at this common junction point to equally excite the four output ports.

Where a coaxial line 11 is employed to excite the junction to, a suitable energy coupling member 19 may be connected to the center conductor 2% of the coaxial line 11 at the common junction point, as shown, which coupling symmetrically excites all four of the outlet ports of the junction with equal power from the microwave input signal and in the same transmission mode, as is desired.

The four outlet ports leading from the junction are each in communication with the inlet to a different microwave switch l2, l3, l4, and 15, with the outlet from each of said switches being adapted to be coupled to a different output channel waveguide (not shown). Thus, the junction together with the four switch arms selectively enables the transmission of the microwave signal over any one of four dilferent output paths as is desired.

According to the present invention, each of the microwave switch arms is of the type that provides a short circuit to the junction when the switch is in tie-energized condition, but when the switch arm becomes energized, it provides a low-loss transmission path from the outlet port and through the switch arm to the channel selected. By this mode of operation it is necessary only to energize that one of the microwave switches that is connected in the output path desired.

It is preferred to employ Faraday effect rotator switches of the type known as tetrahedral switches wherein a microwave is transmitted through the switch only when the plane of polarization of the microwave entering the switch from the hybrid junction is rotated within the switch by As best shown in FIG. 2, one preferred switch of this type comprises a short section of waveguide 21 containing a pencil or rod shaped element 22 of ferrite or other material that is active in the Faraday magneto-optical mode through the section. The pencil or element 22 is of greater length than its diameter and is provided with a magnetizing winding 23 wound in a generally cylindrical configuration about the element 22 to provide a magnetic field lengthwise through the ferrite. When the magnet coil 23 is energized to produce a sufficient magnetic field strength through the rod 22, a microwave entering the waveguide section from the hybrid junction is rotated to displace its plane of polarization by 90 at the outlet of the waveguide section 21.

The tetrahedral type switch is further characterized in having a constant cross-sectional area through all positions along its length but having adjoining side dimensions progressively and equally increase and decrease in dimension from the inlet area to the outlet area of the waveguide section. As a result the inlet opening of the waveguide section and the outlet opening thereof are identical in cross sectional area and dimensions but are effectively angularly displaced from one another by 90 As is characteristic of waveguide propagation of microwaves, the a or horizontal broad side dimension of the guide must be sufiiciently wide to propagate a wave of given frequency, whereas the vertical or b side must be dimensioned sutficiently to prevent propagation of a wave with the E vector perpendicular thereto. Consequently, each of the tetrahedral ferrite switches are provided with inlet dimensions that are chosen to propagate the microwave signal at the frequency originating from the junction. However, in a direction along the length of each switch arm, the a or horizontal dimension progressively decreases in size to normally prevent this microwave from passing down the guide, and instead the wave is normally blocked from passing down this section and the switch accordingly presents a short-circuit to the junction. However, when the magnet winding 23 is energized, the magnetized ferrite pencil effectively and progressively rotates the plane of polarization of the microwave by 90 whereby as the wave travels down the guide, the horizontal side a dimension at the outlet becomes equal in length to the vertical side b at the inlet and the vertical side b at the outlet of the waveguide section becomes equal in length to the a" dimension at the inlet. Consequently the progressively varying dimensions of the guide effectively provide a rotation of the waveguide dimensions from the inlet to the outlet by 90 and permit the passage of a microwave whose plane of polarization has been shifted by 90 by means of the energized ferrite pencil 22. Thus, by selectively energizing the magnet winding 23 in any one of the switch arms selected, the microwave signal is propagated from the junction and through that energized switch arm but is prevented from passing through any of the other switch arms. Upon de-energizing that magnet winding 23, the rotation of the microwave is prevented and the switch arm prevents the continued passage of the wave thereby to again present a short-circuit to the hybrid junction.

Although not illustrated, the ferrite pencil 22 may be centrally supported in the waveguide section 21 by a suitable dielectric supporting means, such as a pair of perforated Teflon beads or the like which engage the inner walls of the waveguide and have a centrally aligned opening therethrough for receiving and supporting opposite ends of the ferrite pencil 22. If desired, these beads may be made porous to provide air circulation therethrough for cooling the ferrite pencil 22; and, if required, forced air cooling may be provided by a suitable fan or the like to circulate the air through the waveguide section 21 and enhance the cooling effect.

For interconnecting the tetrahedral switch arms with the junction 10 with the various switch arms in alignment with the outlet ports of the junction, rectangular or circular connecting flanges as shown at 26 in FIG. 1 or at 24 in FIG. 2, may be provided at the inlet of each switch, which flanges are adapted to be bolted or otherwise suitably fastened to the junction through aligned openings 28, 29 or other means. A similar flange construction such as 27 in FIG. 1 or in FIG. 2 may be provided at the outlet end of each waveguide switch arm section 21 for coupling the switch arm to a waveguide transmission path or to other transmission or utilization means as desired.

FIG. 3 generally illustrates in block diagram form an electrical system for selectively energizing the different ones of the electromagnets in the various switch arms for selectively energizing the switch. As shown, each of the electromagnets such as 23a, 23b, 23c and 23d, in the four switch arms, may be each energized by a driver circuit 3%), 31, 32, and 33, respectively, which driver circuit produces a necessary pulse of power to sufficiently energize the ferrite arms. In one preferred construction, the electromagnet windings 23 each may be provided by a coil consisting of seven turns wrapped directly over the ferrite pencil. The driver circuit 3 produces a power pulse having a voltage from six to thirty volts and a current of rorn seventy-five to fifteen amperes, respectively.

The driver circuits 30 to 33, inclusive, are preferably power type, one-shot multivibrators that are adapted to be selectively triggered by a suitable triggering source indicated at 34, for producing a constant waveform power impulse to actuate the electromagnet coils 23. One preferred driver circuit is illustrated in H6. 4 and comprises a pair of silicon control rectifiers having characteristics similar to those of a gas thyratron. As is known to those skilled in the art, silicon control rcctifiers operate in the manner of a rectifier once they are triggered but are modified to block power flow in the forward direction until the rectifier is triggered by the application of a triggering impulse of usually about one volt. After the rectifiers are triggered, they conduct in the forward direction with a very low forward voltage drop. Control rectifiers of this type are available with an average current extending to about 50 ampcres.

Referring to FIG. 4 for consideration of one preferred driver circuit according to the invention, a pair of silicon control rectifiers are both connected with the positive electrodes thereof, 48 and 43, adapted to be energized by a positive source of voltage through current-limiting resistors 52 and 51, respectively. The positive electrodes 4t) and 43 are also interconnected by a storage capacitor 46 to provide feedback operation as hereafter described. In the one-shot multivibrator configuration, the first silicon control rectifier is adapted to be triggered by the input triggering signal received over line 35 and passing to its control electrode 42. Upon receiving this triggering impulse, the rectifier commences conduction and passes current from its positive electrode 40 to its negative electrode 41 and thence through its associated electromagnet switch coil 23a and a current limiting resistor 53 to ground 39. Paralleling the elcctromagnet coil 23a and resistor 53 is preferably connected a Zener-type diode 55 and a series connected resistor 54 for the purpose of preventing any excessive transient rise of voltage across electromagnct coil 23a.

Upon receiving the triggering impulse at control electrode 42, the silicon control rectifier 40, 41 conducts to energize the electromagnet winding 23a, thereby to operate its associated microwave switch arm (FIGS. 1 and 2). The associated silicon control rectifier 43, 44 is not energized by the trigger pulse over line 35 and hence does not become conducting. The conduction of the first rectifier creates a voltage drop across resistor 52, thereby creating a potential difference across storage capacitor 46 to charge the storage capacitor 46 in such fashion as to progressively raise the potential at the control electrode 45 of the second or companion silicon control rectifier 43, 44. After the passage of a given period of time determined by the time constants of the circuit comprising the storage capacitor 46 and the resistor 51, the voltage across storage capacitor 46 increases sufiiciently to reduce the potential across the first silicon control rectifier 40, 4-1 and thereby extinguish or prevent further conduction through this rectifier. Concurrently, the voltage across storage capacitor 46 is discharged to increase the voltage charge on capacitor 48 connected between the control electrode 45 of the second silicon control rectifier and ground, sufiiciently raising the potential to trigger the second silicon control rectifier 43, 44 into conduction. This latter conduction, discharges the storage capacitor 46 to its initial uncharged condition while at the same time, the control capacitor 48 becomes discharged through resistor 49 to ultimately extinguish the second silicon control rectifier 43, 44. Consequently upon the application of each input triggering impulse over line 35, the one-shot power multivibrator is triggered into operation to energize electromagnet coil 23a with SLlffiClBIli power to operate the microwave switch arm and thereafter the multivibrator is automatically extinguished and reset to respond to the next succeeding triggering input pulse.

FIG. illustrates, in line diagram form, one manner of cascading a plurality of microwave switches of FIG. 1 to provide a commutating system having 32 different output channels. As shown, one manner of providing the 32 output channels is by cascading eleven of such microwave multipole switches in three connected banks or layers. In the first layer, the input microwave signal is conveyed to the first junction 56, represented as a horizontal line and from this junction 56 may be transmitted over any one of the four channels 57, 53, 59 or 66 as indicated by the numbered dots shown. Only two of these channels, 57 and 60 are employed in this configuration and the two remaining channels 58 and 59 are not utilized. From the two channels 57 and 60, the microwave signal is thence directed to second and third hybrid junctions 61 and 66, respectively, which in turn are each provided with four output channels, numbered 62, 63, 64, and 6S; and 67, 68, 69 and '79, respectively. Each of these latter four output channels are in turn directed to a diiferent junction 71 to 78, inclusive, in a third bank, and with each of the junctions in the third bank having four output channels as shown to provide a total of thirtywo output channels.

Tracing the passage of a microwave signal through the three banks to any one of the thirty-two output channels, the microwave signal being directed to the first junction 56 is, for example, first transmitted over channel 57 by selective operation of the first multipole switch. From channel 57, the signal is thence transmitted to the second junction 61 which is also selectively energized to transmit a microwave signal over the transmission path numbered 63, for example, leading to the junction '72 in the third bank. The junction 72 in the third bank is then selectively energized to further transmit a microwave signal over channel 79, for example, to the output path desired. Because of the very low loss associated with each multiple switch, it has been found that in an arrangement such as shown in FIG. 5, an insertion loss of only approximately one decibel is obtained from the input junction 56 to the output channel '79 or to any of the other of the thirty-two output channels.

Although but one preferred embodiment of the invention has been illustrated and described by way of example, it is believed evident to those skilled in the art that many variations and substitutions may be made without departing the spirit and scope of the invention. Accordingly, this invention is to be considered as being limited only according to the following claims.

What is claimed is:

l. A microwave commutator for selectively interconnecting a microwave from a single inlet to any one of a plurality of outlets comprising: a turnstile junction having four outlet ports, and an inlet port, a coaxial transmission line and coupler means interconnected with said inlet port for introducing and coupling a microwave signal to said turnstile to equally excite all of said outlet ports within the junction, the central axis of each of said out- .3 let ports lying in a common geometric plane and intersecting at a central junction point within the junction, and the central axis of the inlet port being perpendicular to said geometric plane and intersecting the said geometric plane at said common junction point within the junction, a plurality of microwave switch arms, each communicating With a different outlet port of said junction, said switches each comprising a waveguide section having a uniform cross-section along its length but having its alternate sides oppositely and equally varying in dimension along its length until at the outlet thereof each side has the same dimensions as the adjacent side at the inlet thereof, an energizable Faraday rotator member within each switch, an electromagnet for each Faraday rotator member energizable to produce a strong magnetic field within said rotator member, and a triggering means for selectively energizing different ones of said electromagnets responsively to an input impulse to vary the plane of polarization of a microwave signal introduced into the energized switch arm by electrical degrees.

2. A multichannel switching system for microwaves comprising: a microwave junction comprising an n-sided cavity having an axial inlet in one of the end walls and a plurality of more than two outlets each disposed in a different side of the cavity disposed to be equally excited by microwave energy received at the inlet, a plurality of microwave switch arms each positioned at a different one of the outlets of the junction, each of the switch arms containing a Faraday effect rotator therein and electrical conductor means for applying a magnetizing force to said rotator, said rotator in each switch arm normally providing a short circuit at the outlet of the junction to prevent transmission of microwaves through the arm and providing a transmission through the arm upon the application of a magnetizing force, and triggering means for selectively applying and removing energization to the electrical conductor means of different ones of the rotator members, thereby to selectively switch microwave energy through only the ditferent ones of the switch arms whose electrical conductor means are energized.

3. A multichannel switching system for microwaves comprising an n-sided cavity having a port in each of the sides and an axial feed in one of the end walls, where n is more than 2, a plurality of single channel switch arms interconnected with said cavity with each switch arm in communication with a difierent port of said cavity, and a triggering means for selectively energizing diiferent ones of said switch arms thereby to direct a signal from said axial feed through only the energized switches, each of said switch arms being comprised of a tetrahedral waveguide section of progressively varying cross-sectional dimensions but constant cross-sectional area and a Faraday effect rotator and winding therein.

4. In the switching system of claim 3, the number of sides 12 being 4.

References Cited by the Examiner UNITED STATES PATENTS 2,459,768 1/49 Cork et al. 333-6 2,644,926 7/53 Varela 333-7 2,867,772 1/59 Allen 3331.1 2,923,903 2/60 Fox 333-24.3 2,941,166 6/60 Meyer 3337 2,980,869 4/61 Rolfs 3337 2,981,688 4/61 Albers-Schecnberg 333-24.3 3,008,098 11/61 Hill et al 33398 3,032,723 5/62 Ring 33,37 3,042,882 7/62 Jamison 333-243 HERMAN KARL SAALBACH, Primary Examiner. 

1. A MICROWAVE COMMUTATOR FOR SELECTIVELY INTERCONNECTING A MICROWAVE FROM A SINGLE INLET TO ANY ONE OF A PLURALITY OF OUTLETS COMPRISING: A TURNSTILE JUNCTION HAVING FOUR OUTLET PORTS, AND AN INLET PORT, A COAXIAL TRANSMISSION LINE AND COUPLER MEANS INTERCONNECTED WITH SAID INLET PORT FOR INTRODUCING AND COUPLING A MICROWAVE SIGNAL TO SAID TURNSTILE TO EQUALLY EXCITE ALL OF SAID OUTLET PORTS WITHIN THE JUNCTION, THE CENTRAL AXIS OF EACH OF SAID OUTLET PORTS LYING IN A COMMON GEOMETRIC PLANE AND INTERSECTING AT A CENTRAL JUNCTION POINT WITHIN THE JUNCTION, AND THE CENTRAL AXIS OF THE INLET PORT BEING PERPENDICULAR TO SAID GEOMETRIC PLANE AND INTERSECTING THE SAID GEOMETRIC PLANE AT SAID COMMON JUNCTION POINT WITHIN THE JUNCTION, A PLURALITY OF MICROWAVE SWITCH ARMS, EACH COMMUNICATING WITH A DIFFERENT OUTLET PORT OF SAID JUNCTION, SAID SWITCHES EACH COMPRISING A WAVEGUIDE SECTION HAVING A UNIFORM CROSS-SECTION ALONG ITS LENGTH BUT HAVING ITS ALTERNATE SIDES OPPOSITELY AND EQUALLY VARYING IN DIMENSION ALONG ITS LENGTH UNTIL AT THE OUTLET THEREOF EACH SIDE HAS THE SAME DIMENSIONS AS THE ADJACENT SIDE AT THE INLET THEREOF, AN ENERGIZABLE FARADAY ROTATOR MEMBER WITHIN EACH SWITCH, AN ELECTROMAGNET FOR EACH FARADAY ROTATOR MEMBER ENERGIZABLE TO PRODUCE A STRONG MAGNETIC FIELD WITHIN SAID ROTATOR MEMBER, AND A TRIGGERING MEANS FOR SELECTIVELY ENERGIZING DIFFERENT ONES OF SAID ELECTROMAGNETS RESPONSIVELY TO AN INPUT IMPULSE TO VARY THE PLANE OF POLARIZATION OF A MICROWAVE SIGNAL INTRODUCED INTO THE ENERGIZED SWITCH ARM BY 90 ELECTRICAL DEGREES. 